Time-temperature dependence of the gamma' phase volume fraction was investigated for a second generation single crystal nickel-based superalloy exposed to very short high temperature regimes (1,100-1,200 degrees C). In this temperature range, the dissolution of the strengthening gamma' phase occurs. Evolution of the gamma' volume fraction in transient regimes has been established for each temperature and activation energy of the dissolution phenomenon were determined. They directly attest from the activity of the diffusing species involved during this phenomenon. From these analyses, the volume fraction at equilibrium was established for the entire temperature range where dissolution occurs. A model, based on a time/temperature equivalence, is proposed to quantify the gamma' volume fraction dissolved during short high temperature exposure.